Depth Sounder Instrument that fits Speedometer Hole?

I am setting up my 1990 Pirata with custom 1000-pound ballast bag under a custom enclosure that replaces the rear seat with the hopes that this set up, combined with suck gate would get me surfing. The enclosure will create a new rear seat above the bag, and additional storage space just forward of the original storage, all covered with a large sun deck platform that will open for storage access.

I am considering adding Perfect Pass or Ride Steady speed control with the control head mounted in one of the original speedometer holes and am seeking a depth sounder display to fit in the remaining speedometer hole. And I haven't found any.

I actually haven't measured my holes yet, but I suspect they are 4" diameter. I haven't found any 4" or similar depth sounders on the market. I am wondering if anyone else has come across a source?

I have not found a depth finder that uses a 4" hole, all of them are 2". Although if you are into vintage you may be able to find an old fish finder from an 80s or earlier 90s bass boat that is 4"